Dragon Search SA Report Tallies Nearly 1,700 Sea Dragon Deaths From South Australia Algal Bloom

A new report compiled by Dragon Search SA has documented nearly 1,700 sea dragon mortalities resulting from the harmful algal bloom that impacted South Australian waters beginning in early 2025, according to findings reported by ABC Australia.

Led by local marine ecologist Janine Baker, the Dragon Search SA assessment analyzed 1,540 citizen science reports submitted by 253 individuals to the iNaturalist platform. The data covered observations of sea dragons, pipefish, and seahorses collected between January 1, 2025, and May 31, 2026.

According to the findings, approximately 1,524 weedy sea dragons and 159 leafy sea dragons were recorded dead across the state. The leafy sea dragon holds the status of South Australia's official marine emblem.

Professor David Booth of the University of Technology Sydney, a member of Dragon Search SA, noted that South Australia serves as a global hotspot for both weedy and leafy sea dragons. He explained that enthusiasts travel internationally to locations such as Rapid Bay to view the animals.

The harmful algal bloom first surfaced in South Australian waters in early 2025. The extended outbreak impacted Encounter Bay, the St Vincent and Spencer gulfs, Investigator Strait, and waters surrounding Kangaroo Island, resulting in widespread marine mortalities and public health concerns.

Sea dragons belong to the Syngnathidae family, which possesses small gill pores easily obstructed by dense microalgae. Because of this anatomical feature, sea dragons are unable to rapidly swim away from patches of water containing high concentrations of the bloom.

The algal bloom's lethal effects extended across 13 species within the family, including seahorses and pipefish. The report documented at least 787 seagrass-dwelling brushtail pipefish mortalities, 574 spotted pipefish deaths, and 42 long-snout pipefish deaths. Thousands of additional dead pipefish were observed in metropolitan seagrass wash-ups but remained uncounted.

Additionally, researchers recorded more than 160 short-head seahorses, alongside smaller numbers of the south-eastern Australian big-belly seahorse. The data showed that pipefish and seahorses primarily washed ashore during the winter and spring of 2025, whereas dead sea dragons continued to be observed from the summer of 2025 through the autumn of 2026.

As sea dragons approach their October breeding season, researchers are exploring methods to enhance population numbers. Professor Booth stated that scientists are investigating strategies such as bringing pregnant males into laboratory settings to hatch eggs and rear fry prior to release.

While laboratory rearing offers higher survival rates, Professor Booth emphasized that such measures depend on repairing damaged marine habitats. The region has experienced extensive destruction of sponges, kelp, seagrasses, and the habitats required by sea dragons and their shrimp prey.

Ongoing remediation efforts include shellfish reef restoration projects across multiple sites and research aimed at restoring roughly 6,000 hectares of seagrass meadows along Adelaide's coastline since the 1950s. Seagrasses function as natural filters for microalgae.

The report highlighted that the full population impact of the harmful algal bloom remains undetermined due to the historic and current absence of official systematic surveys. Historical data largely derived from divers, snorkellers, beachgoers, independent surveys, museums, fishers, and trawler bycatch dating from the 1980s to the 2000s.

Janine Baker stated that leafy sea dragon numbers in inshore habitats have declined compared to pre-bloom levels, though offshore populations outside of dived locations remain undocumented. Since the spring of 2025, citizen science divers across seven South Australian areas have documented live sea dragon records in near-shore locations.

Professor Booth noted that while sea dragons have been reported in Second Valley, surveying at Rapid Bay has been restricted by the ongoing closure of the old jetty and its 20-metre diving exclusion zone.

Serving as a sea dragon specialist on the International Union for Conservation of Nature, Professor Booth noted that weedy sea dragons are classified as vulnerable on the red list for species facing higher extinction risks, while leafy sea dragons are categorized as of least concern.